Method and apparatus for decorative etching of surfaces

Abstract

Method and apparatus for decorating by selective etching of a sheet of glass or other etchable workpiece with a stream of high velocity abrasive particles that strike against a surface portion to be etched. The workpiece is supported on a stand over an opening through which abrasive particles are propelled against the workpiece. A hopper located below the opening and spaced therefrom contains a quantity of the abrasive particles and a gaseous stream is directed upwardly from the bottom of the hopper toward the opening to carry abrasive particles at relatively high velocity toward the opening. A filter is interposed in a space between the top of the hopper and the top of the stand, and is adapted to permit the passage of gas while filtering out abrasive particles entrained in the gas. In order to assure that the opening is covered either by a glass sheet or other means when the apparatus is in operation, a safety means is provided so that the gaseous stream is directed through the hopper only when the opening is covered.

What is claimed is: 
     
       1. Apparatus for etching a workpiece such as a sheet of glass or the like with abrasive particles that are propelled against a surface portion of the workpiece, comprising: a stand with a generally horizontal workpiece support at the top thereof;   means defining an opening in said support over which a portion of said workpiece may be placed;   a hopper located below said opening, spaced from said support and adapted to contain a quantity of said abrasive particles;   fluid pressure means including a nozzle mounted in said hopper for directing a gaseous stream at relatively high velocity upwardly through said hopper toward said opening whereby abrasive particles in said hopper become entrained in said stream and are carried thereby toward said opening to strike said surface portion of said workpiece;   filter means interposed between the top of said hopper and said workpiece support and defining an open space between said opening and said hopper whereby gases may pass therethrough outwardly from said space and said abrasive particles entrained in said gases will be filtered out;   movable shield means adapted to be selectively positioned over said opening and being movable between a retracted position and a protective operating position closely spaced above said opening; and   means responsive to said shield means whereby said gaseous stream is directed through said hopper only when said opening is in its protective operating position.   
     
     
       2. Apparatus as defined in claim 1, wherein said filter means comprises an open-celled polymeric foam material. 
     
     
       3. Apparatus as defined in claim 2, wherein said open-celled plastic foam material is a polyether urethane foam. 
     
     
       4. Apparatus as defined in either of claims 2 or 3, wherein said filter means comprises a block of said open-celled polymeric foam with a central opening aligned with said opening in said workpiece support. 
     
     
       5. Apparatus as defined in claim 1, wherein said workpiece support includes a layer of resilient polymeric material positioned on top thereof and adapted to provide a cushioned support for a workpiece positioned thereon. 
     
     
       6. Apparatus as defined in claim 5, wherein said layer of resilient polymeric material comprises an open-celled foam. 
     
     
       7. Apparatus as defined in claim 1, wherein said movable shield means comprises a relatively flat horizontally oriented safety shield member located above said workpiece support and movable between a raised position spaced above a workpiece located on said support and a lowered position overlying said opening and adapted to engage the top surface of a workpiece located on said support and to clamp said workpiece in place preparatory to actuation of said fluid pressure supply means. 
     
     
       8. Apparatus as defined in claim 7, wherein said safety shield is moved between its raised position and its lowered position by fluid means operatively associated with said fluid pressure means. 
     
     
       9. Apparatus as defined in claim 8, wherein said fluid pressure means comprises an air cylinder with a piston operatively connected to said safety shield member. 
     
     
       10. Apparatus as defined in claim 9, wherein said means responsive to said shield means comprises pressure relief means adapted to prevent flow of air to said nozzle while air pressure from said fluid pressure supply means is operating said air cylinder to move said safety shield to its lowered position, and to permit flow of air to said nozzle after said air cylinder is completely actuated to result in a higher pressure in said pressure supply means. 
     
     
       11. Apparatus for etching a workpiece such as a sheet of glass or the like with abrasive particles that are caused to strike a surface portion of the workpiece, comprising: a stand with a generally horizontal workpiece support at the top thereof;   means defining an opening in said support;   a hopper located below said opening spaced from said support and adapted to contain a quantity of said abrasive particles;   fluid pressure means including a nozzle mounted at the bottom of said hopper for directing a gaseous stream at relatively high velocity upwardly through said hopper toward said opening whereby abrasive particles in said hopper become entrained in said stream and are carried thereby toward said opening to strike said surface portion of said workpiece; and   a block of open-celled polymeric foam material interposed between the top of said hopper and said workpiece support and having an opening therethrough aligned with said hopper and said opening in said workpiece support whereby gases may pass through said block outwardly from said opening and said abrasive particles entrained in said gases will be filtered out.   
     
     
       12. Apparatus as defined in claim 11, wherein said foam material is a polyether urethane foam.